Hydraulic control and hydraulic drive coiled tubing tractor

Abstract

The invention provides a hydraulic control and hydraulic drive coiled tubing tractor. The problems that an existing tractor is complex in structure and low in control stability are solved. The first piston cylinder, the second piston cylinder and the third piston cylinder are sequentially arranged on the center pipe in the length direction of the center pipe. Connecting rod supporting mechanisms are arranged at the ends, away from the second piston cylinder, of the first piston cylinder and the third piston cylinder, and the first piston cylinder and the third piston cylinder are used for controlling the two connecting rod supporting mechanisms to be folded and unfolded alternately; the first piston cylinder and the second piston cylinder are installed on the center pipe, the third piston cylinder is installed on a piston rod of the second piston cylinder, a hydraulic control driving assembly used for controlling the first piston cylinder, the second piston cylinder and the third piston cylinder to move is installed on the outer wall of the center pipe, and a drilling fluid inlet is formed in the side wall of the center pipe and communicated with the liquid inlet end of the hydraulic control driving assembly. The single telescopic hydraulic cylinder is adopted, the traction period is shortened, the traction speed is increased, meanwhile, only the pressure of drilling fluid needs to be controlled in the traction process of the tractor, and the system operation stability is high.

Description

Technical Field

[0001] The invention relates to the field of oil and gas well engineering, in particular to a hydraulically controlled, hydraulically driven continuous oil pipe tractor. Background Art

[0002] In the process of oil exploration and development, coiled tubing technology is widely used due to its high efficiency and flexibility, but this technology has the following problems: on the one hand, the borehole diameter is small, the downhole coiled tubing does not rotate, and it is difficult to carry the cuttings at the bottom of the well, resulting in increased friction of the coiled tubing downhole; on the other hand, the coiled tubing has a small diameter and low material strength. When the coiled tubing slides into the bottom drilling tool assembly downhole, the friction between the coiled tubing and the well wall is large. When the axial pressure applied to the coiled tubing is less than the friction between the coiled tubing and the well wall, the downhole coiled tubing is prone to "buckling and self-locking", making it difficult to go down the well, especially when drilling high-angle wells, directional wells, horizontal wells, and deep wells. The extension length is limited, which restricts the promotion and application of coiled tubing drilling technology. Up to now, coiled tubing drilling technology is often used in directional well drilling operations with small axial friction or milling operations with small drilling pressure such as drilling bridge plugs, and its application in horizontal wells is relatively rare. In order to improve the extension capability of coiled tubing drilling horizontal wells, foreign countries have successively carried out research on friction and drag reduction tools and processes, but the extension length is still limited. Conventional friction and drag reduction technology can no longer effectively solve the technical difficulties of coiled tubing horizontal well drilling extension. Unlike conventional technology, the coiled tubing tractor provides axial tension to the coiled tubing to prevent the downhole tool from "buckling and self-locking", thereby increasing the extension length of coiled tubing drilling horizontal wells.

[0003] Currently, the commonly used tractors are generally divided into three types according to their structural design and movement mode: one is the wheeled tractor, which presses the drive wheel onto the casing by tightening the tensioning arm, and relies on the continuous rotation of the drive wheel to drive the tractor forward; the second is the crawler tractor, which contacts the well wall through the crawlers on both sides of the fuselage, and relies on the friction of the crawlers to drive the robot to move; the third is the telescopic tractor, which uses two sets of alternately opening and contracting grippers to alternately open and grip and contract to release the casing or well wall, and the thruster continuously advances and resets to provide continuous traction. Telescopic tractors are divided into electric control and hydraulic control according to the control method, and hydraulic drive and electric drive according to the drive method. It is difficult to insert cables into large-displacement horizontal wells, and long-distance cables will occupy valuable underground space, and the transmission signal is unstable, which is prone to underground accidents. Therefore, hydraulic-controlled hydraulic drive has a wider range of applications and more advantages than electric control and electric drive. At present, most telescopic tractors adopt a double telescopic cylinder structure design, which is too long and has limited ability to pass through curved well sections. In addition, the double telescopic structure makes the tractor's single traction cycle longer and the traction speed slower. In addition, the hydraulic-controlled hydraulic drive system has technical problems such as complex structure and low control stability. Summary of the invention

[0004] The purpose of the present invention is to provide a hydraulically controlled, hydraulically driven coiled tubing tractor, which is used to solve the technical problems of the existing tractors having complex structures and low control stability.

[0005] A hydraulically controlled, hydraulically driven coiled tubing tractor comprises a central tube, and first, second and third piston cylinders sequentially arranged on the central tube along the length direction of the central tube;

[0006] The first and third piston cylinders are both provided with connecting rod support mechanisms at one end away from the second piston cylinder, and the first and third piston cylinders are used to control the two sets of connecting rod support mechanisms to be folded and expanded alternately;

[0007] The first and second piston cylinders are installed on the central tube, the third piston cylinder is installed on the piston rod of the second piston cylinder, a hydraulically controlled drive assembly for controlling the movement of the first piston cylinder, the second piston cylinder and the third piston cylinder is installed on the outer wall of the central tube, a drilling fluid inlet is opened on the side wall of the central tube, and the drilling fluid inlet is connected to the liquid inlet end of the hydraulically controlled drive assembly.

[0008] Optionally, a return spring is disposed in the cylinder body of the first and third piston cylinders at one end away from the second piston cylinder.

[0009] Optionally, the hydraulically controlled drive assembly includes a pressure switch valve, and an output end of the pressure switch valve is respectively connected to a first control module and a second control module;

[0010] The first control module includes a first reset valve, a first sequence valve and a first reversing valve whose inlet and outlet liquid ends are connected in sequence; the liquid outlet end of the first reset valve is also connected to the cylinder body of the first piston cylinder close to the second piston cylinder, and the liquid outlet end of the first reversing valve is connected to the cylinder body on the second piston cylinder;

[0011] The second control module includes a second reset valve, a second sequence valve and a second reversing valve, the inlet and outlet liquid ends of which are connected in sequence. The liquid outlet end of the second reset valve is also connected to the cylinder body of the third piston cylinder close to the second piston cylinder, and the liquid outlet end of the second reversing valve is connected to the cylinder body on the other side of the second piston cylinder.

[0012] Optionally, the liquid outlet end of the first sequence valve is also connected to the first reversing valve, the second reset valve and a control end of the second reversing valve;

[0013] The liquid outlet end of the second sequence valve is also communicated with the other control ends of the first reversing valve and the second reversing valve and one control end of the first reset valve.

[0014] Optionally, a first stroke valve and a second stroke valve are respectively installed in the cylinder bodies on both sides of the second piston cylinder;

[0015] The liquid outlet end of the first reversing valve is also connected to the liquid inlet end of the first stroke valve, the liquid outlet end of the first stroke valve is connected to the other control end of the second reset valve, the liquid outlet end of the second reversing valve is also connected to the liquid inlet end of the second stroke valve, and the liquid outlet end of the second stroke valve is connected to the other control end of the first reset valve.

[0016] Optionally, the first reset valve, the first sequence valve and the first reversing valve, the first reversing valve, the second reset valve and the second reversing valve are all two-position three-way valves.

[0017] Optionally, the connecting rod support mechanism includes a support arm and a support base mounted on the outer wall of the central tube;

[0018] The support arm is connected to the support base via a driven connecting rod, and the support arm is connected to the piston rods of the first and third piston cylinders via a driving connecting rod. Both ends of the driven connecting rod and the driving connecting rod are hingedly connected.

[0019] Optionally, the first piston cylinder comprises a first cylinder body and a first piston rod, and a first piston head is installed at one end of the first piston rod located in the first cylinder body;

[0020] The first piston head slides along the inner wall of the first cylinder, the two ends of the first cylinder are installed on the outer wall of the center tube, the first piston rod and the first piston head are both slidably sleeved on the outer wall of the center tube, the return spring is sleeved on the outer wall of the first piston rod in the first cylinder, and the connecting rod support mechanism is located at one end of the first piston rod extending out of the first cylinder.

[0021] Optionally, the second piston cylinder comprises a second cylinder body and a second piston rod, and a second piston head is mounted on one end of the second piston rod located in the second cylinder body;

[0022] The second piston head slides along the inner wall of the second cylinder, both ends of the second cylinder are installed on the outer wall of the center tube, the second piston rod and the second piston head are both slidably sleeved on the outer wall of the center tube, and one end of the second piston rod close to the third piston cylinder extends out of the second cylinder, and the third piston cylinder is installed on the second piston rod.

[0023] Optionally, the third piston cylinder comprises a third cylinder body and a third piston rod, and a third piston head is installed at one end of the third piston rod located in the third cylinder body;

[0024] The third piston head slides along the inner wall of the third cylinder body, both ends of the third cylinder body are installed on the outer wall of the piston rod of the second piston cylinder, the third piston rod and the third piston head are both slidably sleeved on the outer wall of the piston rod of the second piston cylinder, the return spring is sleeved on the outer wall of the third piston rod in the third cylinder body, and the connecting rod support mechanism is located at one end of the third piston rod extending out of the third cylinder body.

[0025] Due to the adoption of the above technical solution, the present invention has the following advantages:

[0026] 1. The overall design of the tractor of the present application is telescopic, which is simpler than the wheel tractor, reduces the maintenance risk caused by the complex structure, and reduces the possibility of accidents in the complex environment of the well. In addition, the connecting rod support mechanism makes the tractor have a wider range of pipe diameter trials.

[0027] 2. This application adopts the structural design of a single telescopic hydraulic cylinder, which shortens the traction cycle and speeds up the traction speed compared to a double telescopic cylinder.

[0028] 3. The traction process of the tractor in this application only needs to control the pressure of the drilling fluid, and does not require complex electromagnetic control and signal transmission. The system operates stably and the control response is fast, avoiding the delay caused by signal transmission and achieving high traction efficiency.

[0029] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings of the present invention are as follows.

[0031] Figure 1 It is a schematic structural diagram of the coiled tubing tractor of the present invention.

[0032] Figure 2 It is a cross-sectional view of the coiled tubing tractor of the present invention.

[0033] Figure 3 For the present invention Figure 2 A partial enlarged view of point A in the middle.

[0034] Figure 4 For the present invention Figure 2 A partial enlarged view of point B in the middle.

[0035] Figure 5 For the present invention Figure 2 A partial enlarged view of point C in the middle.

[0036] Figure 6 This is a diagram of the traction process of the coiled tubing tractor of the present invention.

[0037] Figure 7 This is a drilling fluid flow diagram of the hydraulically controlled drive assembly of the present invention.

[0038] In the figure: 1-center pipe; 101-drilling fluid inlet; 2-first piston cylinder; 201-first cylinder body; 202-first piston rod; 203-first piston head; 204-first return spring; 205-upper hydraulic cylinder end cover; 206-upper base; 3-second piston cylinder; 301-second cylinder body; 302-second piston rod; 303-second piston head; 4-third piston cylinder; 401-second cylinder body; 402-second piston rod; 403-second piston head; 404-second return spring ;405-lower hydraulic cylinder end cover;406-lower base;5-connecting rod support mechanism;501-support arm;502-support base;503-driven connecting rod;504-driving connecting rod;6-hydraulic drive assembly;601-pressure switching valve;602-first reset valve;603-first sequence valve;604-first reversing valve;605-second reset valve;606-second sequence valve;607-second reversing valve;608-first stroke valve;609-second stroke valve;610-filter. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0040] Embodiment 1:

[0041] like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 A hydraulically controlled, hydraulically driven coiled tubing tractor is shown, comprising a central tube 1, and a first piston cylinder 2, a second piston cylinder 3 and a third piston cylinder 4 which are sequentially arranged on the central tube 1 along the length direction of the central tube 1;

[0042] The first piston cylinder 2 and the third piston cylinder 4 are both provided with a connecting rod support mechanism 5 at one end away from the second piston cylinder 3, and the first piston cylinder 2 and the third piston cylinder 4 are used to control the two groups of connecting rod support mechanisms 5 to alternately expand and fold;

[0043] The first piston cylinder 2 and the second piston cylinder 3 are installed on the central tube 1, the second piston cylinder 3 is installed on the piston rod of the second piston cylinder 3, a hydraulically controlled drive component 6 for controlling the movement of the first piston cylinder 2, the second piston cylinder 3 and the third piston cylinder is installed on the outer wall of the central tube 1, a drilling fluid inlet 101 is opened on the side wall of the central tube 1, and the drilling fluid inlet 101 is connected to the liquid inlet end of the hydraulically controlled drive component 6.

[0044] like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5As shown, the first piston cylinder 2 comprises a first cylinder body 201 and a first piston rod 202, and a first piston head 203 is installed at one end of the first piston rod 202 located in the first cylinder body 201;

[0045] The first piston head 203 slides along the inner wall of the first cylinder body 201, and the two ends of the first cylinder body 201 are installed on the outer wall of the center tube 1. The first piston rod 202 and the first piston head 203 are both slidably mounted on the outer wall of the center tube 1. The first return spring 204 is mounted on the outer wall of the first piston rod 201, and the first return spring 204 is located in the first cylinder body 201. The connecting rod support mechanism is located at one end of the first piston rod 202 extending out of the first cylinder body 201.

[0046] In this embodiment, one end of the first cylinder body 201 close to the second piston cylinder 3 is screwed to a boss of the central tube 1, and the other end of the first cylinder body 201 is installed with an upper hydraulic cylinder end cover 205 and an upper base 206, and the first piston rod 202 slides through the upper hydraulic cylinder end cover 205 and the upper base 206, and an O-ring is arranged between the upper hydraulic cylinder end cover 205 and the side wall of the first cylinder body 201.

[0047] like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, the second piston cylinder comprises a second cylinder body 301 and a second piston rod 302, and a second piston head 303 is installed at one end of the second piston rod 302 located in the second cylinder body 301;

[0048] The second piston head 303 slides along the inner wall of the second cylinder body 301, and the two ends of the second cylinder body 301 are installed on the outer wall of the center tube 1. The second piston rod 302 and the second piston head 303 are both slidably mounted on the outer wall of the center tube 1, and the end of the second piston rod 302 close to the third piston cylinder 4 extends out of the second cylinder body 301.

[0049] In this embodiment, a placement cavity 304 is provided at one end of the second cylinder body 301 close to the first hydraulic cylinder 2, and the hydraulic control drive component 6 is arranged in the placement cavity 304. The end of the second cylinder body 301 close to the first hydraulic cylinder 2 is screwed to another boss of the central tube 1, and a telescopic hydraulic cylinder end cover 305 is installed at one end of the second cylinder body 301 close to the third hydraulic cylinder 4. The second piston rod 302 slides through the telescopic hydraulic cylinder end cover 305, and an O-ring is provided between the second piston rod 302 and the telescopic hydraulic cylinder end cover 305.

[0050] like Figure 1 , Figure 2 , Figure 3 , Figure 4and Figure 5 As shown, the third piston cylinder 4 comprises a third cylinder body 401 and a third piston rod 402, and a third piston head 403 is installed at one end of the third piston rod 402 located in the third cylinder body 401;

[0051] The third piston head 403 slides along the inner wall of the third cylinder body 401, and both ends of the third cylinder body 401 are installed on the outer wall of the piston rod of the second piston cylinder 3. The third piston rod 402 and the third piston head 403 are both slidably sleeved on the outer wall of the piston rod of the second piston cylinder 3. The third spring 404 is sleeved on the outer wall of the third piston rod 401, and the third spring 404 is located in the third cylinder body 401. The connecting rod support mechanism is located at one end of the third piston rod 402 extending out of the third cylinder body 401.

[0052] In this embodiment, one end of the third cylinder body 401 close to the second piston cylinder 3 is screwed to a boss of the second piston rod 302, and the other end of the third cylinder body 401 is installed with a lower hydraulic cylinder end cover 405 and a lower base 406. The third piston rod 402 slides through the lower hydraulic cylinder end cover 405 and the lower base 406, and an O-ring is arranged between the lower hydraulic cylinder end cover 405 and the side wall of the third cylinder body 401.

[0053] In this embodiment, a through hole is provided on the side wall of the cavity on the side where the return spring is provided in the first cylinder body 201 and the third cylinder body 401, and the gas in the well enters the cavity on the side where the return spring is provided in the first cylinder body 201 and the third cylinder body 401 through the through hole. The cylinder body on the side without the return spring of the first piston cylinder 2 is defined as the first hydraulic cavity, the cylinder body on the side without the return spring of the third piston cylinder 4 is defined as the second hydraulic cavity, the cylinder body on the side of the second piston cylinder 3 close to the first piston cylinder 2 is defined as the third hydraulic cavity, and the cylinder body on the side of the second piston cylinder 3 close to the first piston cylinder 2 is defined as the fourth hydraulic cavity.

[0054] like Figure 6 As shown in (a)-6(e), the specific steps of traction by the tractor are: S1: the hydraulically controlled drive component 6 fills liquid into the first hydraulic chamber, the connecting rod support mechanism 5 at one end of the first piston cylinder 2 is stretched open and contacts the well wall, and at the same time the second hydraulic chamber is depressurized, and the connecting rod support mechanism 5 at one end of the third piston cylinder 3 is folded and does not contact the well wall; S2: the hydraulically controlled drive component 6 fills liquid into the third hydraulic chamber, and the second piston rod 302, the third piston cylinder 4 and the connecting rod support mechanism 5 at the front end of the third piston cylinder 4 are pushed downward; S3: the hydraulically controlled drive component 6 fills liquid into the second hydraulic chamber, and the connecting rod support mechanism 5 at the front end of the third piston cylinder 4 is stretched open and contacts the well wall; S4: the first hydraulic chamber is depressurized, and the connecting rod support mechanism 5 at one end of the first piston cylinder 2 is folded and does not contact the well wall; S5: the hydraulically controlled drive component 6 fills liquid into the fourth hydraulic chamber, and the second cylinder body 301, the first piston cylinder 2 and the connecting rod support mechanism 5 at the front end of the first piston cylinder are stretched downward; repeat steps S1-S5 to realize the forward traction of the tractor.

[0055] like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, the connecting rod support mechanism 5 includes a support arm 501 and a support base 502 installed on the outer wall of the central tube 1;

[0056] The support arm 501 is connected to the support base 502 via a driven connecting rod 503, and the support arm 501 is connected to the first piston rod 102 and the third piston rod 302 via a driving connecting rod 504. Both ends of the driven connecting rod 503 and the driving connecting rod 504 are hinged.

[0057] In this embodiment, the support base 502 is fixedly mounted on the central pipe 1, and the first piston rod 102 and the third piston rod 302 both slide through the support base 502. When the first piston rod 102 or the third piston rod 302 is ejected, under the action of the driven connecting rod 503 and the driving connecting rod 504, the support arm 501 contacts the well wall to achieve support at one end. The connecting rod support mechanism 5 of the present application can achieve support of wellbore of any width within its stroke width, and has a wide range of applications.

[0058] like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, the hydraulic control drive assembly 6 includes a pressure switch valve 601, and the output end of the pressure switch valve 601 is respectively connected to a first control module and a second control module;

[0059] The first control module includes a first reset valve 602, a first sequence valve 603 and a first reversing valve 604, the liquid inlet and outlet ends of which are connected in sequence; the liquid outlet end of the first reset valve 602 is also connected to the first hydraulic chamber, and the liquid outlet end of the first reversing valve 604 is connected to the third hydraulic chamber;

[0060] The second control module includes a second reset valve 605, a second sequence valve 606 and a second reversing valve 607 whose inlet and outlet liquid ends are connected in sequence. The liquid outlet end of the second reset valve 605 is also connected to the second hydraulic chamber, and the liquid outlet end of the second reversing valve 607 is connected to the fourth hydraulic chamber.

[0061] like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, a first stroke valve 608 and a second stroke valve 609 are respectively installed in the cylinder bodies on both sides of the second piston cylinder 3;

[0062] The liquid outlet end of the first reversing valve 604 is also connected to the liquid inlet end of the first stroke valve 608, the liquid outlet end of the first stroke valve 608 is connected to the other control end of the second reset valve 605, the liquid outlet end of the second reversing valve 607 is also connected to the liquid inlet end of the second stroke valve 609, and the liquid outlet end of the second stroke valve 609 is connected to the other control end of the first reset valve 602.

[0063] In this embodiment, the first reset valve 602, the first reversing valve 604, the second reset valve 605 and the second reversing valve 607 are all two-position three-way valves, and are all provided with a pressure relief port. The conduction pressure of the pressure switch valve 601 is P0, and the conduction pressure of the first sequence valve 603 and the second sequence valve 606 is P1. A filter 610 is provided at the front end of the pressure switch valve 601. When the tractor moves forward, Figure 7 (a)- Figure 7 (h) Figure 7 The red line in the middle is the flow direction of drilling fluid), and the specific steps are:

[0064] S1: Control the drilling fluid pressure in the central pipe 1 to make it greater than P0, the pressure switch valve 601 is turned on, and the drilling fluid enters the first hydraulic chamber through the filter 610, the pressure switch valve 601 and the first reset valve 602 (the inlet and outlet of the first reset valve 602 are turned on at the initial moment), so that the connecting rod support mechanism 5 at the front end of the first piston cylinder 2 is opened and contacts the well wall.

[0065] S2: When the connecting rod support mechanism 5 at the front end of the first piston cylinder 2 is opened and contacts the well wall, the pressure at the inlet end of the first sequence valve 603 rises and when it is greater than P1, the first sequence valve 603 is turned on:

[0066] The drilling fluid pushes the first reversing valve 604 to change direction through the control end of the first reversing valve 604, and the inlet and outlet liquid ends of the first reversing valve 604 are connected; at the same time, the drilling fluid pushes the second reset valve 605 and the second reversing valve 607 to change direction through the control ends of the second reset valve 605 and the second reversing valve 607, so that the inlet and outlet liquid ends are not connected, and the liquid outlet end is connected to the pressure relief end. Under the action of the second reset spring 404, the second hydraulic chamber is depressurized through the second reset valve 605.

[0067] S3: The drilling fluid enters the third hydraulic chamber through the inlet and outlet of the first reversing valve 604, and the fourth hydraulic chamber is depressurized through the second reversing valve 607;

[0068] S4: When the second piston head 303 moves to the end of its stroke, the first stroke valve 608 is pushed to be turned on, and the drilling fluid passes through the first stroke valve 608 to the control end of the second reset valve 605 to push it to move, so that the inlet and outlet ends of the second reset valve 605 are connected;

[0069] S5: The drilling fluid enters the second hydraulic chamber through the inlet and outlet of the second reset valve 605, so that the connecting rod support mechanism 5 at the front end of the third piston cylinder 4 is opened and contacts the well wall;

[0070] S6: When the connecting rod support mechanism 5 at the front end of the third piston cylinder 4 is opened and contacts the well wall, the pressure at the inlet end of the second sequence valve 606 rises. When it is greater than P1, the second sequence valve 606 is turned on:

[0071] The drilling fluid pushes the second reversing valve 607 to change direction through the control end of the second reversing valve 607, and the inlet and outlet liquid ends of the second reversing valve 607 are connected; at the same time, the drilling fluid pushes the first reset valve 602 and the first reversing valve 604 to change direction through the first reset valve 602 and the control end of the first reversing valve 604, so that the inlet and outlet liquid ends are not connected, and the liquid outlet end is connected to the pressure relief end. Under the action of the first reset spring 204, the first hydraulic chamber is depressurized through the first reset valve 602.

[0072] S7: The drilling fluid enters the fourth hydraulic chamber through the inlet and outlet of the second reversing valve 607, and the third hydraulic chamber is depressurized through the first reversing valve 604;

[0073] S8: When the second piston head 303 moves to the end of its other stroke, the second stroke valve 609 is pushed to be turned on, and the drilling fluid passes through the second stroke valve 609 to the control end of the first reset valve 602 to push it to move, so that the inlet and outlet of the first reset valve 602 are connected;

[0074] S9: Repeat steps S1-S8 to achieve forward traction of the tractor.

[0075] The traction process of the tractor in the present application only needs to control the pressure of the drilling fluid, and does not require complex electromagnetic control and signal transmission. The system operates stably and the control response is fast, avoiding the delay caused by signal transmission and achieving high traction efficiency.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A hydraulically controlled, hydraulically driven coiled tubing tractor, characterized in that: It includes a central tube, and first, second and third piston cylinders sequentially arranged on the central tube along the length direction of the central tube; The first and third piston cylinders are both provided with connecting rod support mechanisms at one end away from the second piston cylinder, and the first and third piston cylinders are used to control the two sets of connecting rod support mechanisms to be folded and expanded alternately; The first and second piston cylinders are installed on the central tube, the third piston cylinder is installed on the piston rod of the second piston cylinder, a hydraulically controlled drive assembly for controlling the movement of the first piston cylinder, the second piston cylinder and the third piston cylinder is installed on the outer wall of the central tube, a drilling fluid inlet is opened on the side wall of the central tube, and the drilling fluid inlet is connected to the liquid inlet end of the hydraulically controlled drive assembly.

2. The hydraulically controlled, hydraulically driven coiled tubing tractor according to claim 1, characterized in that: A return spring is disposed in the cylinder bodies of the first and third piston cylinders at one end away from the second piston cylinder.

3. The hydraulically controlled, hydraulically driven coiled tubing tractor according to claim 1, characterized in that: The hydraulic drive assembly comprises a pressure switch valve, and the output end of the pressure switch valve is respectively connected to a first control module and a second control module; The first control module includes a first reset valve, a first sequence valve and a first reversing valve whose inlet and outlet liquid ends are connected in sequence; the liquid outlet end of the first reset valve is also connected to the cylinder body of the first piston cylinder close to the second piston cylinder, and the liquid outlet end of the first reversing valve is connected to the cylinder body on the second piston cylinder; The second control module includes a second reset valve, a second sequence valve and a second reversing valve, the inlet and outlet liquid ends of which are connected in sequence. The liquid outlet end of the second reset valve is also connected to the cylinder body of the third piston cylinder close to the second piston cylinder, and the liquid outlet end of the second reversing valve is connected to the cylinder body on the other side of the second piston cylinder.

4. The hydraulically controlled, hydraulically driven coiled tubing tractor according to claim 3, characterized in that: The liquid outlet end of the first sequence valve is also connected to the first reversing valve, the second reset valve and a control end of the second reversing valve; The liquid outlet end of the second sequence valve is also communicated with the other control ends of the first reversing valve and the second reversing valve and one control end of the first reset valve.

5. The hydraulically controlled, hydraulically driven coiled tubing tractor according to claim 4, characterized in that: A first stroke valve and a second stroke valve are respectively installed in the cylinder bodies on both sides of the second piston cylinder; The liquid outlet end of the first reversing valve is also connected to the liquid inlet end of the first stroke valve, the liquid outlet end of the first stroke valve is connected to the other control end of the second reset valve, the liquid outlet end of the second reversing valve is also connected to the liquid inlet end of the second stroke valve, and the liquid outlet end of the second stroke valve is connected to the other control end of the first reset valve.

6. The hydraulically controlled, hydraulically driven coiled tubing tractor according to claim 5, characterized in that: The first reset valve, the first sequence valve, the first reversing valve, the first reversing valve, the second reset valve and the second reversing valve are all two-position three-way valves.

7. The hydraulically controlled, hydraulically driven coiled tubing tractor according to claim 1, characterized in that: The connecting rod support mechanism includes a support arm and a support base mounted on the outer wall of the central tube; The support arm is connected to the support base via a driven connecting rod, and the support arm is connected to the piston rods of the first and third piston cylinders via a driving connecting rod. Both ends of the driven connecting rod and the driving connecting rod are hingedly connected.

8. The hydraulically controlled, hydraulically driven coiled tubing tractor according to claim 2, characterized in that: The first piston cylinder comprises a first cylinder body and a first piston rod, and a first piston head is installed at one end of the first piston rod located in the first cylinder body; The first piston head slides along the inner wall of the first cylinder, the two ends of the first cylinder are installed on the outer wall of the center tube, the first piston rod and the first piston head are both slidably sleeved on the outer wall of the center tube, the return spring is sleeved on the outer wall of the first piston rod in the first cylinder, and the connecting rod support mechanism is located at one end of the first piston rod extending out of the first cylinder.

9. A hydraulically controlled, hydraulically driven coiled tubing tractor according to claim 1 or 2, characterized in that: The second piston cylinder comprises a second cylinder body and a second piston rod, and a second piston head is installed at one end of the second piston rod located in the second cylinder body; The second piston head slides along the inner wall of the second cylinder, both ends of the second cylinder are installed on the outer wall of the center tube, the second piston rod and the second piston head are both slidably sleeved on the outer wall of the center tube, and one end of the second piston rod close to the third piston cylinder extends out of the second cylinder, and the third piston cylinder is installed on the second piston rod.

10. The hydraulically controlled, hydraulically driven coiled tubing tractor according to claim 2, characterized in that: The third piston cylinder comprises a third cylinder body and a third piston rod, and a third piston head is installed at one end of the third piston rod located in the third cylinder body; The third piston head slides along the inner wall of the third cylinder body, both ends of the third cylinder body are installed on the outer wall of the piston rod of the second piston cylinder, the third piston rod and the third piston head are both slidably sleeved on the outer wall of the piston rod of the second piston cylinder, the return spring is sleeved on the outer wall of the third piston rod in the third cylinder body, and the connecting rod support mechanism is located at one end of the third piston rod extending out of the third cylinder body.

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